Process for producing high octane gasoline



Nov. 7, 1967 L. E. DREHMAN ETAL 3,351547 PROCESS FOR PRODUCING HIGH OCTANE GASOLINE Filed Nov. 29. 1965 2 Sheets-Sheet 1 INI/NTORS L. E. om-:HMAN H.J. HEPP ATTORNEYS EOmaou/Nolmvai HolvNollovad Nm 1mm v fom Nov. 7, 1967 1 E, DREHMAN TAL 3,351,547

PROCESS FOR PRODUCING HIGH OCTANE GASOLINE A TTORNEVS United States Patent O 3,351,547 PROCESS EUR PRDUCING HIGH OCTANE GASLINE Lewis E. Drehman and Harold J. Hepp, Bartlesville,

Gkla., assignors to Phillips Petroleum Company, a

corporation of Delaware Filed Nov. 29, 1965, Ser. No. 510,250 2 Claims. (Cl. 20S- 62) This invention relates to a process for upgrading gasoline boiling range hydrocarbons to high octane motor fuel.

In one plant process, gasoline boiling range hydrocarbons (B.P. 175-300 F.) are upgraded to a motor fuel having a research octane number of 80 with 3 cc. of tetraethyl lead. The feed stream is reformed and fractionated to separate the C8 and heavier hydrocarbons and the lighter fraction is solvent extracted with an alkylene glycol to recover -aromatics and principally benzene as an extract stream and C7 and lighter hydrocarbons, paralinic and naphthenic hydrocarbons, as a raffinate stream, and the raflinate stream is fractionated to recover the C7s as a bottoms fraction for motor fuel and a C6 overhead fraction.

This invention is concerned with a process for further upgrading the stream of C7 hydrocarbon bottoms fraction.

Accordingly, it is an object of the invention to provide an improved process for upgrading a stream of gasoline boiling range hydrocarbons to produce a high octane .motor fuel. A further object is to provide a process for producing high octane motor fuel from a stream of gasoline boiling range hydrocarbons, which converts more of said hydrocarbons to high octane components than in present plant processes. Other objects of the invention will become apparent to one skilled in the art Iupon consideration of the accompanying disclosure.

The improved process of the invention comprises isomerizing the recovered C7 stream of hydrocarbons downstream of the reforming and solvent extraction steps at relatively low temperature to form C7 isomers of high octane value lboiling below about 190 F., fractionating the isomerizateinto a lighter fraction consisting principally of dimethylpentanes and other hydrocarbons boiling in `the range of 175-190 F., an intermediate fraction boiling in the range of 190-205 F. containing the lower octane isomers, and a heavier fraction boiling above 205 F. The intermediate fraction is recycled to the isomerization step to isomerize the components thereof to higher octane Aisomers Vand the heavier fraction is recycled to the reforming step to convert the components thereof to the higher octane components of the lighter fraction obtained downsream of the isomerization zone.

In another embodiment of the process of the invention, non-reformed C7 hydrocarbons are isomerized, and the isomerizate is fractionated into a lighter fraction consisting principally of dimethylpentanes and other hydrocarbons boiling in the range of 175-190 F., an intermediate fraction boiling in the range of 190205 F. for recycle to the isomerization zone, and -aheavier fraction boiling above 205 F. that is charged to the low-end-point reformer.

The invention is best illustrated and described with reference to the accompanying schematic drawing of which FIGURE 1 is a flow of la plant process in which gasoline boiling range hydrocarbons are upgraded to high octane motor fuel and FIGURE 2 is a flow of another embodiment of a portion of the plant process.

Referring to FIGURE 1, a feed stream of gasoline hydrocarbons boiling in the range of about 175 to 300 F. is fed thru line 10 to low-end-point reformer 12. This loW-end-point reformer is conventional in the art and 3,351,547 Patented Nov. 7, 1967 ICC utilizes a catalyst such as platinum on alumina or other active reforming catalyst. The reformate is passed thru line 14 to ya fr-actionator 16 where the C8 and heavier hydrocarbons boiling above about 212 or 215 F. are recovered as a bottoms fraction thru line 1S and the lower boiling hydrocarbons (B.P. to 212 F.) are recovered as an overhead fraction thru line 20. The stream in line 18 is a motor fuel blending stock.

The overhead stream in line 20 consisting of C7 and lighter hydrocarbons is passed to solvent extraction unit 22 where it is solvent extracted with .an alkylene glycol, preferably diethyleneglycol or a diethylene glycol-triethylene glycol-water mixture, to recover an extract stream in line 24 comprising aromatics (principally benzene) and a ratinate stream in line 26 comprising principally C7 and lower parans and naphthenes. The. raliinate stream is passed from line 26 into a fractionator 28 wherein a separation is made to take the C6 and lighter hydrocarbons overhead thru line 30 and the C7 and higher boiling hydrocarbons in the bottoms stream thru line 32. In fractionator 28 the cut point is about 180 F., the overhead fraction boiling in the range of 1Z0-180 F., and the 'bottoms fraction boiling above 180 F. and consisting essentially of C7 hydrocarbons.

Prior to the improvement of this invention, the C7 stream in line 32 was recovered thru line 34 as a motor fuel having a research octane number of 80 with 3 cc. of TEL therein. In accordance with the invention, the C7 stream in line 32 is passed thru lines 36 and 38 to isomerizing zone 40 where this stream is isomerized at relatively low temperatures in cont-act with a highly active isomerization catalyst to high octane isomers, particularly, those boiling at a temperature below 190 F. The isomerizing step is effected at temperatures not exceeding 350 F. such as in the range of 15G-350 F. and preferably in the range of 20D-350 F. A highly active isomerization catalyst such as .acidic platinum-promoted alumina or silica-alumina or AlCla-HCl plus isobutane as an inhibitor, is used in the isomerization step. Another catalyst which is effective is a noble metal-boria-alumina composite. These catalysts are conventional in the art and need no further description. Pressure in the isomerization zone is maintained in the range of 50-1000 p.s.i.g. and preferably in the range of 20G-600 p.s.i.g. Space velocity is maintained in the range of 0.5 to 10 weight of feed per hour per weight of catalyst. The isomerization may be effected in the presence of hydrogen and when used, an amount of hydrogen in the range of 0.01 to 15 moles, preferably 1 to 8 moles, per mole of feed is used. The isomerization step converts the feed stream to almost thermodynamic equilibrium composition at low temperatures (below about 350 F.) where dimethylpentanes are favored isomers.

The isomerizate is passed thru line 42 into fractionator 44 where a separation is made into a bottoms stream recovered thru line 46 and an overhead stre-am recovered thru line 48. The heavier stream in line 46 comprising principally methylcyclohexane and normal heptane is recycled to line 10 as a portion of the feed to the low-endpoint reformer 12. The cut point in fractionator 44 is about 200 F., the overhead stream containing hydrocarbons boiling rbelow 200 F. The lighter stream in line 48 comprising principally dimethylpentanes with lesser Aamounts of 2,2,3-trimethylbutane, cyclohexane, 1,1-dimethylcyclopentane, 2-methylhexane, 3-methylhexane, 1,3-dimethylcyclopentane and 1,Z-dimethylcyclopentane, is passed into fractionator 50 `for separation into an overhead stream recovered in line 52 boiling in the range of to 190 F. and containing the lighter and higher octane C7 isomers, particularly dimethylpentanes, and a heavier fraction recovered in line 54 and recycled to line 38 Where it is mixed with the feed to isomerization zone 40 for conversion to desirable isomers. The stream recovered thru line S4 has a boiling range of 190 to 200 F. and contains the heavier dimethylpentanes of lower octane value and is the intermediate cut of the isomerizate in line 42.

Referring to FIGURE 2, corresponding elements and lines are correspondingly numbered. The main difference between the liow of this figure and the flow of FIGURE 1 is that C7 isomerization and subsequent fractionation precedes rather than follows reforming. The fractionation downstream of isomerizer 40 is substantially and materially different from that in FIGURE 1 in that the lighter and higher octane hydrocarbons are recovered as overhead from fractionator 44 in line 60, the intermediate fraction is recovered as overhead from fractionator 50 thru line 64 and recycled to line 15 for mixing with the fresh feed in line 13 passing to the isomerization zone 40,

and the heavier fraction is recovered as a bottoms stream g from fractionator 50 in line 66. This bottoms stream is fed to the low-end-point reformer 12, or is optionally hydrodealkyl'ated to yield mainly cyclohexane.

When operating with the arrangement illustrated in FIGURE 2, fractionator 44 is operated so `as to make a cut at 190 F., the lower boiling hydrocarbons comprising the overhead stream in line 60 and the higher boiling hydrocarbons comprising the bottoms stream in line 62. Fractionator 50 is controlled so 'as to make a cut at about 205 F., recovering an intermediate fraction of the isomerizate boiling below 205 F. for recycle to the isomerization zone and a heavier fraction boiling above 205 F. as the stream in line 66 for recycling to the reformer.

The following examples illustrate different aspects of the invention and are not to be construed as unnecessarily limitin-g the invention.

TABLE I Volume b.p.d.

Line No.

Before With Increase Invention Invention The above volumes demonstrate the effectiveness of the invention as compared to plant operation before theinvention. The stream in line 52 is a high octane motor fuel having a RON-l-3 ml. TEL of 95 There is also an increase in motor fuel blending stock in line 1S. Thus, the invention upgrades a substantial part of the fuel stream in line 32 from 80 RON+3 ml. TEL to 95+RON-l-3 ml. TEL and increases the amount of blending fuel produced from 4250 to 4780 barrels per day.

EXAMPLE II In utilizing the isomerization step and the recovery steps of FIGURE 2, 7000 barrels per day of a fresh feed consisting of a narrow-boiling range fuel comprising principally C7 paraflins, naphthenes, and aromatics, are processed. This stream is separated from the l75-300 F. gasoline boiling range hydrocarbons by using fractionator 16 to separate a stream 13 having a boiling range TABLE II Stream No., Barrels/Day Symbol The components represented by A include cyclohexane, 2,2-dimethylpentane, 2,4-dimethylpentane, `and 2,2,3-tri- 35 meth-ylbutane. B represents 3,3-dimethylpentane. C represents 1,l-dimethylcyclopentane. D includes 2,3-dimethylpentane, Z-methylhexane, S-methylhexane, 1,3-dimethylcyclopentane, and trans-1,2-dimethylcyclopentane. E is 3-ethylpentane. F is normal heptane. G includes methylcyclohexane and cis-1,2-dimethylcyclopentane. H represents ethylcyclopentane and trimethylcyclopentanes. I represents dimethylhexanes `and toluene is the .T component.

The process illustrated in Example II produces a relatively pure methylcyclohexane concentrate. This stream in line 66 can be recycled to the reformer, as shown, to yield 3180 barrels per day of high octane gasoline (98 RON-l-3 ml. TEL). When the process is operated in this Way the total yield of high octane gasoline is thus 6785 barrels per day, including stream 60. Alternatively, when cyclohexane is the desired product, the stream in line 66 can be hydrodealkylated to yield 1790 barrels per day of cyclohexane. The products other than cycloheXane from Ithe hydrodealkylation are combined with stream 60 to yield 3900 barrels per -day of high octane gasoline (98 RON-l-B ml. TEL).

In another embodiment of the invention, the stream in line 42 of FIGURE l is subjected to the downstream separation (fractionation) steps of FIGURE 2. In this embodiment, stream 66 is fed to reformer 12, stream 64 is recycled to isomerization zone 40, and stream 60 is recovered as the high octane gasoline product.

Likewise, the stream in line 42 of FIGURE 2 may be fractionated in accordance with the fractionation illustrated in FIGURE 1.

The isomerization step is preferably operated'a-t the lowest possible temperature since the nal products, i.e., dimethylpentanes and methylcyclohexane are thermodynamically favored at low temperatures. Temperatures substantially below 350 F. are preferred. Another catalyst suitable for low temperature isomerization is the HF-l-BFS catalyst system.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

We claim:

1. A process for upgrading a hydrocarbon stream consisting principally of a mixture of Ce-C, hydrocarbons including a substantial amount of n-*heptane which comprises the steps of:

(1) reforming said mixture to produce an eluent s-tream containing paraiiins, naphthenes, and aromatics including benzene;

(2) fractionating the effluent stream of step (1) to recover an overhead stream of principally C7 and lighter hydrocarbons and a bottoms stream of principally C8 and heavier hydrocarbons;

(3) solvent extracting the overhead stream of step (2) to recover an 'aromatic extract stream of principally benzene eand -a rainate stream of principally paraf- 15 nic and naphthenic of C6-C7 hydrocarbons;

(4) fractionating the ranate stream of step (3) to recover an overhead stream of principally C6 hydrocarbons and a bottom stream of principally C7 hydrocarbons including substantially all of the n-heptane in said ranate stream;

(5) isomerizing the bottoms stream of step (4) at a temperature in the range of `200 to 350 F. to principally a stream of C, 'branched chain isomers;

(6) fractionating the isomerizate from step (5) into a lighter stream comprising hydrocarbons boiling below about 190 F. as a high octane motor fuel, an intermediate stream boiling in the range of about 190 to 200 F., and a heavier stream boiling above about 200 F.;

(7) recycling the heavier stream of step (6) to step (1); and

(S) recycling the intermediate stream of step (6) to step (5) to form higher octane isomers thereof.

2. The process of claim 1 wherein the feed stream in step (1) is a stream of 175-300o E gasoline, the cut point in step (2) is about 212 F. and the cut point in step (4) is about 180 F.

References Cited UNITED STATES PATENTS 8/1960 Hennig 208-65 9/ 1961 Gerhold et al 20864 

1. A PROCESS FOR UPGRADING A HYDROCARBON STREAM CONSISTING PRINCIPALLY OF A MIXTURE OF C6-C7 HYDROCARBONS INCLUDING A SUBSTANTIAL AMOUNT OF N-HEPTANE WHICH COMPRISES THE STEPS OF: (1) REFORMING SAID MIXTURE TO PRODUCE AN EFFLUENT STREAM CONTAINING PARAFFINS, NAPHTHENES, AND AROMATICS INCLUDING BENZENE; (2) FRACTIONATING THE EFFLUENT STREAM OFSTEP (1) TO RECOVER AN OVERHEAD STREAM OF PRINCIPALLY C7 AND LIGHTER HYDROCARBONS AND A BOTTOMS STREAM OF PRINCIPALLY C8 AND HEAVIER HYDROCARBONS: (3) SOLVENT EXTRACTING THE OVERHEAD STREAM OF STEP (2) TO RECOVER AN AROMATIC EXTRACT STREAM OF PRINCIPALLY BENZENE AND A RAFFINATE STREAM OF PRINCIPALLY PARAFFINIC AND NAPHTHENIC OF C6-C7 HYDROCARBONS: (4) FRACTIONATING THE RAFFINATE STREAM OF STEP (3) TO RECOVER AN OVERHEAD STREAM OF PRINCIPALLY C6 HYDROCARBONS AND A BOTTOM STREAM OF PRINCIPALLY C7 HYDROCARBONS INCLUDING SUBSTANTIALLY ALL OF THE N-HEPTANE IN SAID RAFFINATE STREAM; (5) ISOMERIZING THE BOTTOMS STREAM OF STEP (4) AT A TEMPERATURE IN THE RANGE OF 200 TO 350*F. TO PRINCIPALLY A STREAM OF C7 BRANCHED CHAIN ISOMERS; (6) FRACTIONATING THE ISOMERIZATE FROM STEP (5) INTO A LIGHTER STREAM COMPRISING HYDROCARBONS BOILING BELOW ABOUT 190*F. AS A HIGH OCTANE MOTOR FUEL, AN INTERMEDIATE STREAM BOILING IN THE RANGE OF ABOUT 190 TO 200*F., AND A HEAVIER STREAM BOILING ABOVE ABOUT 200*F.; (7) RECYCLING THE HEAVIER STREAM OF STEP (6) TO STEP (1); AND (8) RECYCLING THE INTERMEDIATE STREAM OF STEP (6) TO STEP (5) TO FORM HIGHER OCTANE ISOMERS THEREOF. 